[PATCH] ntfs: fix panic about slab-out-of-bounds caused by ntfs_listxattr()

[Zeng Heng]

Here is a BUG report from syzbot:

BUG: KASAN: slab-out-of-bounds in ntfs_list_ea fs/ntfs3/xattr.c:191 [inline]
BUG: KASAN: slab-out-of-bounds in ntfs_listxattr+0x401/0x570 fs/ntfs3/xattr.c:710
Read of size 1 at addr ffff888021acaf3d by task syz-executor128/3632

Call Trace:
 ntfs_list_ea fs/ntfs3/xattr.c:191 [inline]
 ntfs_listxattr+0x401/0x570 fs/ntfs3/xattr.c:710
 vfs_listxattr fs/xattr.c:457 [inline]
 listxattr+0x293/0x2d0 fs/xattr.c:804

Fix the logic of ea_all iteration. When the ea->name_len is 0,
return immediately, or Add2Ptr() would visit invalid memory
in the next loop.

Fixes: be71b5cba2e6 ("fs/ntfs3: Add attrib operations")
Reported-by: syzbot+9fcea5ef6dc4dc72d334@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Zeng Heng <zengheng4@xxxxxxxxxx>
---
 fs/ntfs3/xattr.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/ntfs3/xattr.c b/fs/ntfs3/xattr.c
index 7de8718c68a9..911e110b8d6e 100644
--- a/fs/ntfs3/xattr.c
+++ b/fs/ntfs3/xattr.c
@@ -178,6 +178,9 @@ static ssize_t ntfs_list_ea(struct ntfs_inode *ni, char *buffer,
 	for (ret = 0, off = 0; off < size; off += unpacked_ea_size(ea)) {
 		ea = Add2Ptr(ea_all, off);
 
+		if (!ea->name_len)
+			break;
+
 		if (buffer) {
 			if (ret + ea->name_len + 1 > bytes_per_buffer) {
 				err = -ERANGE;
-- 
2.25.1